Issues concerning passenger safety have become increasingly important as the speed of the vehicles transporting these passengers has increased. Over time, the most significant source of passenger injuries has involved the rapid deceleration of the vehicle due to a frontal collision.
In an attempt to reduce injuries due to frontal vehicle collisions, several devices are known which allow the vehicle seat to move in response to the sudden deceleration of the vehicle.
U.S. Pat. No. 5,022,707, issued to Beauvais et al., discloses an improved passenger restraint apparatus wherein, in response to deceleration of the vehicle, the seat moves such that both a forward and a rearward portion of the seat move forward and upward with the forward portion of the seat moving upward faster than the rearward portion of the seat. This specific seat motion provides enhanced passenger restraint for frontal collision over the prior devices including moving seats.
However, collisions from the rear of the vehicle are also common and can cause serious injuries. And, as the orientation of the passenger and of the passenger support with respect to a given acceleration has a profound impact upon the effectiveness of any device designed to restrain the passenger, devices designed to respond to frontal collisions are not easily adapted to use in rear collision situations. This is true as, in most vehicles, the orientation of the passengers and the passenger supports (the seats) is highly asymmetric relative to the front and rear of the vehicle.
In a forward collision, the most significant problems which a restraint device is designed to eliminate are the pitching forward of the upper body, and the consequent contact between the passenger's head and the dash, the steering wheel, the windshield or the front seat backs, and submarining of the passenger.
However, in a rearward collision the primary concerns are neck whip, excessively forceful or improperly oriented contact with a head restraint, ramping up the seat back and ejection backward over or, in the case of collapse of the seat, through the seat back.
In addition, the anatomical characteristics of the front and rear surfaces of a human being are substantially different. Therefore, those contact areas which are suitable for restraining the passenger in the event of a rear collision are quite different from those suitable for restraining the passenger in the event of a frontal collision.
Thus there is a need for a device which provides effective passenger restraint and which is effective for collisions from the rear of the vehicle.